Uranium is machined much as other metals for a variety of purposes. The scraps or chips of uranium created by machining present a disposal problem: because of the nature of uranium the chips cannot be simply discarded as other less chemically active metals. Further, the cost of uranium metal and the cost of disposal of it make the recovery and recycling of the chips extremely attractive.
Because uranium readily ignites and burns, oil is not favored as a lubricant in machining. Typically a water-based lubricant is used, but this introduces another set of problems. Most reprocessing techniques for uranium use heat and vacuum. But uranium reacts with water in the presence of heat to form free hydrogen, which presents the very real potential for fierce hydrogen fires and explosions. Centrifuges do not remove enough of the water to solve the problem. Introducing the chips into a melt is also unsatisfactory because of the danger that the water carried by the chips will turn to steam in the melt and cause an explosion and because the steam can break into hydrogen and oxygen, causing even more violent explosions. Further, the presence of water in vacuum melting furnaces prevents the attainment of adequate vacuum levels necessary for safe melting. Pieces of similar metals such as magnesium, titanium, zirconium and other metals in the shape of chips, scraps or other forms suffer from similar problems.